Metal casting machines

ABSTRACT

A metal casting machine of the kind equipped with a highfrequency electric induction melting unit that includes a crucible to which the stock is supplied in billet form; in which the crucible is made in situ by blowing, resin-bonded powdered refractory material into a preformed mold cavity established in the structure of the melting unit, and subjecting the molded crucible to the action of a gaseous hardening agent.

United States Patent [7 2] lnventors Edward C. Bishop Bromsgrove; Roland P. Chapman, Reddltch; John W.

Coleman, Northlield, all of England [21 Appl. No. 842,549

[22] Filed July 17, 1969 [45] Patented Dec. 7, 1971 [73] Assignee The Brltlsh Motor Corporatlon Llmlted Blrmlngham, England [3 2] Priority Aug. 6, 1968 [33] Great Britain [54] METAL CASTING MACHINES 6 Claims, 5 Drawing Figs.

[52] U.S. Cl 164/201, 25/2, 164/43 [51] Int. Cl 1122c 15/24 [50] Field of Search 164/33, 43, 138, 200, 201, 202; 25/2 [56] References Cited UNITED STATES PATENTS 2/1938 Billand 2,661,513 12/1953 Brewer 164/200 2,770,855 11/1956 Phillips" 164/200 X 2,899,724 8/1959 Peterson.... 164/202 2,911,691 11/1959 Peterson.... 164/202 2,942,319 6/1960 Anthony.... 164/33 X 3,030,675 4/1962 Chiabotti 164/200 3,458,613 7/1969 Andrews et a1. 164/43 X FOREIGN PATENTS 7,610 12/1959 Japan 164/16 Primary Examiner.1. Spencer Overholser Assistant Examiner-John E. Roethel v Artorney-Holcombe, Wetherill & Brisebois ABSTRACT: A metal casting machine of the kind equipped with a high-frequency electric induction melting unit that includes a crucible to which the stock is supplied in billet form; in which the crucible is made in situ by blowing, resin-bonded powdered refractory material into a preformed mold cavity established in the structure of the melting unit, and subjecting the molded crucible to the action of a gaseous hardening agent.

PATENTEDUEC 7l97l 3625-278 SHEET 1 [IF 3 PATENTEDDEE 71971 I 34625278 SHEET 3 or 3 METAL CASTING MACHINES This invention relates to metal casting machines of the kind equipped with a high frequency electric induction melting unit that includes a crucible to which the stock is supplied in billet rorm, and, in particular, is concerned with improvements in the production of melts in such machines.

According to this invention, in a metal casting machine of the kind specified above, the crucible (which is used for only one melt and then replaced by a fresh one) is made in situ by blowing, i.e. by a blast of compressed air, resin-bonded powdered refractory material into a prefonned mould cavity established in the structure of the melting unit, and subjecting the moulded crucible to the action of a gaseous hardening agent. In effect, therefore, the arrangement is such that an automatic moulding machine for producing the one-melt disposable crucible is combined with the melting unit as a single entity.

The invention obviates various disadvantages associated with conventional methods of melting metals in casting machines. Apart from eliminating the maintenance procedure of relining melting pots, the use of a one-melt disposable crucible also eliminates the problem of slag control. For these reasons, in contrast to the conventional practice, the invention lends itself to automation of metal casting. Referring to the accompanying drawings:

FIG. 1 is a sectional elevation of a metal casting machine (comprising a combined crucible-moulding and metal melting assembly) embodying the invention, and shows the machine with its core raised preparatory to starting the initial operation of moulding a crucible;

FIG. 2 is a part-sectional elevation of the machine with its core in the operative position, and shows how the crucible is blown;

FIG. 3 is a view similar FIG. 2 and shows the blown crucible ready to be treated by a gaseous hardening agent;

FIG. 4 is a fragmentary view, partly in section, showing the finished crucible charged with metal billets to be melted; and

FIG. 5 is a schematic plan view, on a greatly reduced scale, of an indexing unit of the combined crucible-moulding and metal casting machine.

Referring to FIG. I, a combined crucible-moulding and metal melting assembly I is supported so that it overlies a platen 2 which can be raised, to the position shown, in order to serve as the temporary bottom closure of a mould cavity which is formed in the assembly 1. Between its outer wall 3 and a ceramic liner 4, the assembly 1 has an annular block 5 of ceramic material in which a coil 6 of high frequency induction heating equipment is embedded. For a purpose which will be explained later, the platen l is fitted with a plunger 7 coaxial with the vertical axis of the assembly I. The remainder of the assembly includes a core 8 which is mounted so that it can be lowered centrally into the hollow space within the liner 4. The core 8 has a central pipe 9'through which a charge of resinbonded sand or powdered ceramic material is blown, by a blast of compressed air, to form the crucible. The pipe 9 is surrounded by an annular duct I0 which has several outlet vents 11 formed in the core 8.

When the core 8 is lowered into the position depicted in FIG. 2, a mould cavity 12 is established by the combination of the core 8, the liner 4, and a temporary bottom closure which is constituted by the upper surface of the platen 1. By means of a standard core-blowing machine (not shown), resinbonded sand 13 is blown down the pipe 9 and into the mould cavity 12 at the rate of approximately 1 lb. per minute, and at a pressure of about 50 psi. As soon as the mould cavity 12 has been completely filled, the blow is stopped automatically.

The plunger 7, which has so far remained inactive with its tip flush with the upper surface of the platen l, is now pushed into the outlet of the pipe 9 (see FIG. 3). This is done in order to prevent the residual sand in the pipe 9 from being afiected by the curing operation to which the moulded crucible 13A now has to be subjected. The curing is effected by a gaseous hardening agent (e.g. carbon dioxide) introduced into the top of the annular duct at a pressure of about 10 p.s.i., for a period of approximately 30 seconds. The gas issues from the outlet vents 11 and permeates the moulded crucible 13A. The tip of the plunger 7 is bevelled to facilitate its entry into a rubber O-ring seal 14 which is located in a retaining groove formed in the inside wall of the pipe 9 near its outlet. When the upper part of the plunger 7 has passed through the seal 14 (see FIG. 3), the gas issuing from the outlet vents II is prevented from acting upon the sand remaining in the pipe 9.

After the hardening of the crucible 13A has been completed the plunger 7 is retracted. The mixture of sand and resin is sufficiently viscous to remain in place in the pipe 9 until the next blow takes place.

The completed crucible 13A has its pouring hole 15 (FIG. 4), which was created partly by the lower end of the pipe 9 and partly by the plunger 7, covered by a mild steel plug 16. The crucible is automatically charged with stock 17 (FIG. 4) comprising two billets; one being of fresh material and the other of material reclaimed from a previous cast. The strength of the resin-bonded crucible 13A is such that its base does not need any extraneous support during the billet-loading operation and the subsequent melting. The heating coil 6 (FIG. 1) is then energized. When the whole of the charge has been melted, the plug 16 fuses and the melt runs out through the pouring hole 15 into a mould (not shown).

The slag, or any inclusion in the melt, collects on the inside wall of the crucible 13A and is retained so that it does not contaminate the casting.

The invention has been devised primarily for use in an auto matic investment casting plant, in which the automatic casting machine comprises, in addition to the above-described crucible-fonning and metal melting assembly, a billet-feeding unit, a crucible-unloading unit and a rotary indexing unit.

The indexing unit just mentioned is indicated at 18 (FIG. 5). It has four indexing arms 19 rigidly fixed to a shaft 20 which is rotatable intermittentlythrough to accommodate four stations A, B, C and D. Each of the indexing arms 19 supports one of the above-described assemblies 1. The operations of blowing the crucible and hardening it take place at station A. After retraction of the plunger 7 (FIG. 3), the completed crucible is then indexed to station B, where it receives its charge. Melting of the charge, and the pouring of the melt to form the required casting, is effected at station C, and the onemelt disposable crucible 13A is removed at station D. Its removal is facilitated by the tapered shape of the liner 4 (FIG. 1

We claim:

1. In a metal casting machine,

a mold having an wall defining the outer wall of a mold cavity, a high-frequency induction heating unit in said wall for heating metal in said mold, and

core means mounted to be lowered into said cavity and,

when so lowered, define the inner wall of said mold cavity,

said core means comprising a first passage through which a resin-bonded refractory powder may be introduced into said cavity to fonn a disposable crucible therein, and a second and separate passage through which a gaseous hardening agent may be introduced into said cavity to harden said crucible, and

means for blocking said first passage off from said cavity when said gaseous hardening agent is to be introduced into said cavity.

2. In combination a metal casting machine as claimed in claim 1, means for introducing said resin bonded powder into said first passage under pressure, and means for introducing said gaseous hardening agent into said second passage under pressure.

3. A metal casting machine as claimed in claim 1 in which said mold comprises a ceramic liner defining the outer wall of mold cavity and a separable-bottom closure.

4. A metal casting machine as claimed in claim 3 in which said ceramic liner is of tapered shape.

5. In a metal casting machine,

a mold having an inner wall defining the outer wall of a mold cavity and heated by a high-frequency induction heating unit, and

core means mounted to be lowered into said cavity and,

when so lowered, define the inner wall of said mold cavity,

said core means comprising a first passage through which a resin-bonded refractory powder may be introduced into said cavity to fonn a disposable crucible therein, and a second and separate passage through which a gaseous l hardening agent may be introduced into said cavity to harden said crucible, and 

2. In combination a metal casting machine as claimed in claim 1, means for introducing said resin bonded powder into said first passage under pressure, and means for introducing said gaseous hardening agent into said second passage under pressure.
 3. A metal casting machine as claimed in claim 1 in which said mold comprises a ceramic liner defining the outer wall of mold cavity and a separable bottom closure.
 4. A metal casting machine as claimed in claim 3 in which said ceramic liner is of tapered shape.
 5. In a metal casting machine, a mold having an inner wall defining the outer wall of a mold cavity and heated by a high-frequency induction heating unit, and core means mounted to be lowered into said cavity and, when so lowered, define the inner wall of said mold cavity, said core means comprising a first passage through which a resin-bonded refractory powder may be introduced into said cavity to form a disposable crucible therein, and a second and separate passage through which a gaseous hardening agent may be introduced into said cavity to harden said crucible, and a plunger extending through the bottom of said mold and movable between a position blocking the outlet end of said first passageway and a position clear of the outlet end of said first passage, whereby said first passage may be blocked when said gaseous hardening agent is introduced, thereby preventing hardening of the resin-bonded refractory powder in said first passage.
 6. A metal casting machine as claimed in claim 5 comprising a resilient O-ring seal within said passage outlet, the tip of said plunger being bevelled to facilitate its entry into said seal. 